A DVS (Digital Vinyl System) has been known as a technology of reproducing digital content.
The DVS includes: a dedicated record disc on which a time code signal is recorded; a signal reproduction device such as a record player and a CD player; an analog-digital convertor such as an audio interface; a computer; and a reproduction output device such as a mixer and a speaker.
The dedicated record disc on which time codes (time information) are recorded is reproduced on the record player. The reproduced time code signal is converted from analog to digital by an audio interface and then outputted to the computer.
The computer extracts audio signals from music piece data being reproduced, adds acoustic effects set on the computer to the extracted audio signals, and outputs the audio signals corresponding to the transmitted time codes to the audio interface.
The audio interface outputs the audio signals inputted from the computer. The mixer outputs the audio signals to a reproduction output device such as a power amplifier and a speaker.
In such a DVS, a performer provides a scratch operation and a pitchbend operation on the record player, so that a time code signal is reproduced according to these operations. Consequently, audio signals according to the operation of the performer can be reproduced and outputted. Moreover, since various acoustic effects can be added to the audio signals in the computer, a DJ performance can make an extremely high dramatic impact.
The invention of Patent Literature 1 discloses a record disc dedicated for use in a DVS, in which right and left time code signals reproducible by a pickup and having the same frequency are recorded in such a condition that phases of the signals are relatively shifted.
In the invention of Patent Literature 1, with use of the shifted-phase right and left time code signals, a reproduction direction in which the record disc is being rotated in a forward direction or in a reverse direction is judged by detecting zero-cross points of one of the right and left time code signals, at which the time code signal is converted from a negative value to a positive value, and by detecting whether a polarity of the other of the right and left time code signals is negative or positive at the detected zero-cross points.